Recently, A non-licensed usage for a TV frequency band that is not used and is vacant, which is called TVWS, is allowed by the Federal Communications Commission (FCC), and as a result, researches on a spectrum sharing technology in the frequency band have been actively conducted internationally. In the IEEE, various working groups, such as IEEE 802.22, 802.11af, and 802.15.4, have completed or are advancing a TVBD or TVBD network self standard. IEEE 802.00 has newly established 802.22 WG at the same pace with a TVWS usage plan by the FCC in November 2004, and completed the physical layer (PHY)/media access control (MAC) standard for a wireless regional area network (WRAN) that is a TV band fixed wireless communication network using the CR technology in 2011.
IEEE 802.19.1 is advancing standard work for an independently applicable TVWS frequency sharing method, without dependence on a radio technology between heterogeneous or independently operated TVBD networks or heterogeneous TVBDs. In order to efficiently use the TVWS and maximize efficiency of limited frequency resources internationally, the establishment of a TVWS usage technology standard has been spurred at a national level.
In order to operate a TVBD network by using the TVWS that is a frequency band which is not used for each region in a specific time within a TV band and is vacant, a top priority is not to exert an interference influence on existing first services operated in a neighboring area. To this end, the TVBD network is operated, by using a usable frequency band (available channel list, hereinafter, an available channel) received from a TVWS database, at a point spaced apart by a predetermined distance (keep-out distance, hereinafter, a protection spaced distance) from a service boundary point of an existing service operated within the TV band. When the TVBD is operated while including the protection spaced distance from a service boundary point of a first user, the first user may smoothly operate the service without being influenced from the TVBD, but the TVBD network may have a reduced service radius due to an interference influence of the first user.
In the related art, when the TVBD desired to use the TVWS notifies the TVWS database of related information, such as location information, a type, and a height of a transmission antenna, of the TVBD through WiFi or an existing network and requests available channel information to the TVWS database, the TVWS database calculates a usable channel at a location which the TVBD desires to currently operate by using information on the first user, location information on the corresponding TVBD, the type of the TVBD, the height of the transmission antenna, a protection spaced distance according to the height of the TVBD transmission antenna, and the like. In this case, the existing TVWS database transmits a calculation result of the available channels usable by the corresponding TVBD to the TVBD without a priority, and the TVBD selects one or multiple channels in the available channel list to operate the TVBD service.
However, when the TVWS database calculates the available channels according to the method in the related art, a service radius of the TVBD network may be decreased due to an influence of the first service operated in an adjacent region.